Such a steam power plant generally contains a number of steam drums, with which steam is generated at different power levels, it being possible to feed said steam to a steam turbine in particular. Impurities in the water/steam circuit of the steam power plant must be removed. The impurities become more concentrated in the respective steam drum. The extraction of saturated steam from the steam drums causes non-volatile substances to remain in the steam drums. These non-volatile substances are removed from the circuit by elutriation. The circuit thereby loses energy and water, which has to be fed back in again in the form of additional water, known as deionized water. This incurs additional costs. It is also an environmental burden.
To keep energy losses low, it has already been proposed that the elutriation water should be transferred from the high-pressure level steam drums to the lower-pressure steam drums, in which it can expand (so-called boiler cascading blowdown). Some of the energy of the additionally introduced elutriation water can then be converted to power by evaporating it and routing the steam thus obtained to the steam turbine. One disadvantage of this is however that all the impurities are transferred from one pressure level to the next.
It is also known that the elutriated water in the steam drum of one pressure level can be expanded in a separator and the water and steam separated. The steam is then transferred at low pressure into a collection tank for degassing and to heat up the water contained therein.